The invention relates to a polymer alloy of a polysulfone and an N-vinyl lactam polymer. The invention relates to fibers made from the alloy and applications of the alloy fiber. One important application is in fiber containing filter structures. Fine fiber materials are known in the prior art. We are aware of Barris et al., U.S. Pat. No. 4,650,506 teaching a method of spinning fine fiber, Kahlbaugh et al., U.S. Pat. No. 5,672,399 teaching a filter structure comprising a separation media and a fine fiber layer in a multilayer structure, and a variety of patents on fine fiber media and filter structures, Chung et al., U.S. Pat. No. 6,743,273; Barris et al., U.S. Pat. No. 6,800,117; Gillingham et al., U.S. Pat. No. 6,673,136; Gogins et al., U.S. Pat. No. 6,716,274; Buettner et al., U.S. Pat. No. 6,740,142; and Benson et al., U.S. Pat. No. 6,746,517.
The art has known for many years that the alloying of polymers to obtain a single glass transition temperature (Tg) material with a homogeneous mixture on a molecular level is difficult and rare. However, such polymer alloys can often obtain important novel properties that can be tailored to specific end uses. Very often the properties of the homogeneous alloy attains the best properties of its individual components. The great majority of polymer mixtures fail to alloy, but forms a two-phase blend after mixing and the mixtures are often characterized by reduced chemical, thermal, physical and structural properties and have two, three or more thermal transition or glass transition temperatures. Further, alloys tend to be transparent and can be processed as though they were single component thermoplastics. While great success has been obtained in the manufacture and use of fine fiber materials in a variety of filtration applications, fine fiber materials can be improved for excellent properties in gaseous or liquid filtration. The materials are improved for use with high temperature stability, and physical and mechanical stability in the presence of organic or aqueous liquids while filtering liquid mobile fluids in filtration applications.
A substantial need exists in the art for such polymer materials in the form of an improved alloy that can be formed into improved nanofiber, microfiber and fine fiber structures. A further substantial need exists for filtration media, filter structures and filtration methods that can be used for removing particulate materials from fluid streams. Fluids streams include both gaseous and liquid streams. Typically gaseous filters are filters for air or industrial waste gas streams. Liquid streams or compositions include aqueous liquids and in particular, non-aqueous liquids such as fuels, lubricating oils and hydraulic fluids. The invention provides such media, filtration structures and methods that are stable to the condition found in filtering gaseous streams, air streams, aqueous and non-aqueous liquid streams. The polymer alloy fiber and provides a unique media or media layer combinations that achieve improved filtration properties including substantial permeability, high wet strength, substantial efficiency and long filtration life.